The invention relates to a roll mill, particularly in the form of a material bed roll mill which is capable for simple and quick replacement of wear protection casings.
Roll mills and material bed roll mills of the aforementioned type are known in various forms. Thus, for example, the general construction and the principle of comminution of material bed roll mills is explained in Duda, CEMENT-DATA-BOOK, Volume 1, 3rd Edition, 1985, for instance pages 255 to 257. A further example of a known roll mill is disclosed in EP-B-0 280 897.
These roll mills are preferably used in instances where relatively brittle mill feed material is to be comminuted in a particularly energy-saving mode of operation, particularly for the comminution of cement raw materials, cement clinker, ore materials, coal and the like. The rolls which are pressed against one another with a relatively high pressing force are each mounted by way of a roll shaft in the vicinity of both ends of the rolls so as to be rotatable by way of bearings in bearing jewels which are heldxe2x80x94so as to be partially movablexe2x80x94in a machine frame. Both rolls are driven either by way of a common drive motor or by way of individual drive means.
In the type of comminution described above, the roll surfaces are subjected to a high degree of wear. For this reason the rolls of these roll mills, particularly of the material bed roll mills, are equipped with outer wear protection casings which after they are worn can be replaced by new or reclaimed wear protection casings. This replacement of the wear protection casings on the rolls necessitates high expenditure of labour and time, quite apart from the fact that during this replacement work the roll mill is out of operation and thus not available for comminution of material.
The object of the invention, therefore, is to create a roll mill, particularly a material bed roll mill in which the construction by comparison with the known mill designs permits particularly simple and rapid replacement of the wear protection casings on the rolls.
This object is achieved according to the invention by the characterizing feature involved for easy replacement of the wear protection casings.
Since in the known roll mill constructionsxe2x80x94as explained abovexe2x80x94each roll is mounted by way of its roll shaft so as to be rotatable in bearings or bearing jewels which are disposed in the machine frame at both ends of the rolls, it is generally necessary to remove the mountings and possibly a part of the machine frame first of all before the actual work for replacement of the wear protection casing of the corresponding roll can be undertaken.
On the other hand, in the roll mill according to the invention the two rolls are only mounted at one end in the machine frame, i.e. the mountings for the roll shaft of each roll are only disposed in the vicinity of one end of the roll, whilst the opposite end of the roll is freely accessible. Thus this means that, when work becomes necessary for replacement of a wear protection casing, the corresponding roll is or both rolls are freely accessible from the opposite end thereof to the mountings; thusxe2x80x94by comparison with the known mill constructionsxe2x80x94the installation work for mountings or parts of the machine frame can be omitted. Merely in this way the expenditure of labour and time for replacement of the wear protection casings on the rolls of a roll mill according to the invention can be significantly reducedxe2x80x94again by comparison with the known constructions.
For reasons of strength, with the relatively high grinding pressures in a roll mill constructed as a material bed roll mill the wear protection casing of each roll is frequently constructed as a closed ring. In this case the construction according to the invention is especially advantageous, since the entire ring-shaped wear protection casing can be replaced in one piece relatively quickly, by comparison with wear protection casings which are made up of segments. It should also be added that ring-shaped wear protection casings can be manufactured particularly inexpensively, thus providing an economical mode of operation of the roll mill.
During the comminuting operation in a material bed roll mill it is known that pressing forces or contact pressures of more than approximately 50 MPa and up to approximately 400 MPa and possibly more occur, and these pressing forces are a function of the nature of the material for comminution and also of the desired comminuting work or the end product. Thus for example the pressing forces during the comminution of cement materials, particularly cement clinker, lie in the upper pressure ranges of the pressing forces mentioned above, whilst for the comminution for example of material from the mining industry (e.g. ore material) pressures in the middle or lower range of the aforementioned pressing forces may be sufficient. Especially for comminuting work with pressing forces which lie in these middle and lower pressure ranges the roll mill according to the invention in the form of a material bed roll mill is particularly advantageous.